1. Field of the Invention
The present invention relates to a boarding bridge for use in boarding and alighting of passengers on airplanes etc.
2. Description of Related Art
Boarding bridges are tunnel-shaped walkways that connect, for example, an airport terminal building and an airplane, to allow direct boarding and alighting of passengers between the terminal building and the airplane.
The intermediate gangway portion of a boarding bridge is constituted by a plurality of telescopically fitted gangway units and extends and contracts by the relative movement of the gangway units in the longitudinal direction. A gangway unit at the distal end is supported by a movable leg equipped with a traveling unit at the lower part. The movable leg travels by means of the traveling unit, so that the intermediate gangway portion extends and contracts or swings about the terminal building side.
Doing so copes with the gap between the terminal building and the airplane or a difference in positional relationship therebetween.
The traveling unit is generally mounted below a horizontally extending support beam provided at the lower part of the movable leg.
As shown in Japanese Unexamined Patent Application, Publication No. 2004-82833, for example, the traveling unit is provided with a rotating table at the center of the support beam (lateral member) so as to rotate about the vertical axis. The rotating table is equipped with an axle mounted at the lower part with a pin and right and left wheels that are rotatably mounted at the ends of the axle. The right and left wheels are configured to be independently rotationally driven via separate driving motors and reducing gears.
This supports only the widthwise central portion; the interval between the right and left wheels is narrow; and the axle is attached to the rotating table with the pin. Therefore, it has problems of low stability in response to a widthwise external force that acts on the boarding bridge, so that the boarding bridge is prone to sway.
To solve these problems, for example, a traveling unit shown in Japanese Unexamined Patent Application, Publication No. 2006-182060 is proposed.
It is provided with support frames that are rotatable about the vertical axis at the lower parts of both ends of the support beam. A horizontally extending axle to which a wheel is fixed is rotatably supported by each support frame. A traveling motor is connected to the extending portion of the axle. Thus, when the traveling motor is driven, the driving wheel rotates about the horizontal axis through the axle and travels. The support frames at both sides are configured to be individually rotated about the vertical axis by the separate motors.
Since the interval between the wheels is substantially equal to the length of the support beam, a long interval between the wheels can be ensured as compared with that of Japanese Unexamined Patent Application, Publication No. 2004-82833. Accordingly, the stability of the boarding bridge can be improved.
The disclosures in Japanese Unexamined Patent Application, Publication No. 2004-82833 and Japanese Unexamined Patent Application, Publication No. 2006-182060 support loads with two wheels. Therefore, the wheels need to be large to carry a heavy load for a heavy-load (for example, long) boarding bridge, which results in high costs.
Moreover, there is a limitation to increasing the size of the wheels, which leads to limiting conditions for manufacturing a very large (for example, very long) boarding bridge.
With the disclosure in Japanese Unexamined Patent Application, Publication No. 2006-182060, the support frames that change the directions of the wheels are separately and independently driven by the separate motors. Therefore, this needs advanced, complicated control to set the rotating angles thereof to appropriate values, and because the driving units are mounted to the each wheel the costs are increased.